TMDL or Total Maximum Daily Limit

What is a TMDL?

The Total Maximum Daily Load Program is a Federal program authorized under the Clean Water Act to address waters that are not meeting water quality standards.

Salem Creek is considered impaired for its uses, The City of Winston-Salem has a TMDL for the reduction of fecal coliform (bacteria) and turbidity (sediment). To achieve this reduction, the City of Winston-Salem has developed a plan which outlines steps to take in public education and outreach, monitoring, assessment, and reporting.

A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. The TMDL is then used to establish limits on sources of the pollutant which are classified as either point sources or non-point sources. Point source is a pollutant that comes from a single, identifiable source, such as a factory or refinery. Non-point source pollution comes from many different sources. Non-point source pollution is caused by rainfall or snowmelt moving over the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally deposing them into lakes, rivers, wetlands, coastal waters and even underground sources of drinking water.

The TMDL load allocation is calculated for all non-point sources that are contributing to the pollution. Depending on the sources identified in the TMDL, the load allocation may apply to septic tanks, fertilizer runoff from agricultural and residential areas, bacteria, or sediment runoff from new construction sites. The TMDL does not have authority in most cases to force a reduction of pollutants from non-point sources. TMDLs are usually only effective at addressing non-point sources when enough interest is present from the community, local government, and water quality advocacy groups to carry out the implementation plan.

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